Surveying instrument



Original application filed July 3, 1928, Serial No. 290,145 Divided and this Patented Dec. 22, 1931 v UNITED STATES J PATENT OFFICE,

EDWARD W. ARMS, OF TROYNEW YORK, ASSIGNOR T0 W. & L. E. GURLEY, OF TROY, 'NE i/V YORK, A CORPORATIGN OF NEW YORK SURVEYING INSTRUMENT This invention relates to geometrical instruments and particularly to transits and other geometrical having similar requirements.

' 1930. Serial frames for 1nstruments The present application is a division of my prior application Serial filed July 3,

1928, which disclosed and claimed the article here claimed, and also the method of manufacturing it. The parent application is now directed to the method of producing frames forgeometncal instruments.

Frames for such mstrument s ordinarily include a base plate supported on a vertical spindle for orientation and standards on said plate on which the telescope is mounted.

Usually the telescope is pivota lly mounted on a horizontal axis which intersects the vertical axis.

In prior constructions the spindle is a separate piece from the base p late and the standards are also a separate piece or pieces.

This sectional construction ha been usedin precision lnstrum these, partly to permit free sele ter1als, and partly to permits heretofore ents such as ction of maadjustments and hand fitting regarded by instrument makers as essential to refined accuracy.

The present invention involves a radical departure in this respect. A virtually integral structure is a unitary and dopted. All

adjustments save one are eliminated. Reliance is placedonthe precision of machine operations. Practical interchangeabilityis initially is .atleast equal to that art instruments, and the main secured. The accuracy. of the instrument of the prior tained accuracy is superior because of the absence of fitted joints with their necessa connections.

rily stressed Generally stated, the desired geometrical relations of the various axes .of the instrument are determined by the machining operations, all'of which axis of the vertical spindle. larly this is accomplished are referred to the p More particuby establishing countersinks bymeans of which the unitary. frame is supportedin a machine tool on the geometrical axis of the spindle surface of rotation (preferably generating a temporary) the piece for mach 7 forms the spindle.

is symmetrical relatively apphcationfiled April- 7, N0. 142,3 31.

about such axis, and thereafter positioning ining' operations by engaging either the countersinks or said surface. If the locating surface betemporary, as preferred, a final operation is to mount the frame in the countersinks and machine the spindle to final form.

above described,"the invention is not limited to any particular type ofunitary sinks and accurately position the spindle blank while the base plate die cast in one piece on or around the mushroom head! By using a suitable aluminum alloy a virtually unitary piece can be, secured including inserted spindle and die cast base plate, and standards, precisely formed and positioned relatively to one another.

Such a unitary frame is free of internal strains, and thus is superior in maintained accuracy to any sectional frame in which the connectors, and indeed to some degree all parts, are subject to continual stress. Moreover the frame is accurately symmetrical with reference to the axis of the insert which The frame so made is machined by operations which preserve the ori inal axis of the spindle insert as the axis of the entire frame; Thus the finished frame to the spindle axis, incident to the use and standards are and no disturbing effects of diverse alloys occur.

In this way the original axis is preserved throughout and used in the final spindle- .finishin'g operation; 'Proper design of fixtures makes it simple to ensure the accurate intersection of the spindle and trunnion axes or the spindle andtelescope axes and the essential 90? relation thereof.

By proceeding as above set forth, the

process being set forth in greater detail in the parent application, there is produced the frame here claimed.

The invention, as embodied in a transit frame, is illustrated in the accompanying drawings in which:

Fig. 1 is a plan view of the completed frame.

Fig. 2 is a view partly in vertical axial section.

Fig. 3 is a fragmentary view of the second trunnion bearing, i. the one not visible in. Fig. 2.

The spindle (3 is produced from a blank of for ed aluminum alloy, preferably a socahed strong aluminum alloy such as described in the patent to Archer and Jefl'ries, No. 1,472,739, granted October 30, 1923. Broadly stated the alloy is free from copper except as an impurity and contains magnesium and not less than 0.5% silicon, preferably about 1% of each of magnesium and silicon. (See the Archer and Jelfries patent, page 1, lines 29 to 35, and lines is to 5%.) This alloy quenched and artificially aged as described in the patent and is therefore in favorable condition for machining operations. 7

The blank is first turned with an over size spindle portion and an enlarged head whose form clearly shown in 2. This includes a conical portion 7, a knurled or ribbed cylindrical rim 8 and a smaller cylindrical portion 9 whose lower face is flush with the lower face 11 of the base plate 12. The countersinlrs on which it is turned re preserved.

The oversiz-zed spindle portion then serves to posit-ion the blank in a casting die in which the base plate telescope standards are cast upon the enlarged head.

Various different forms m it be adopted fo this enlarged head, that chosen being des nod to offer several angles and a roughened peripheral surface, all of which favorable to close c'ageinent with the die casting formed around the The V0 parts do not fuse together, but the shrink of the die cast metal is such as produce a bond which will stand severe abuse. For example, the joint may be struck heavy blows with a machinist hammer while the frame supported by clamping th spindle in a vise, without showing tendency of the joint to fail. Blows 1 ch break out pieces of the base plate do not affect the bond between the fo a; and he di i Generally staed, the alloy casting is an aluminum alloy containing as the main alloying constituent about 12% con. Iron also present in small quantity but is re an impurity. (see the patent to ilenrics and Archer No. 1,508.556, page line 59 ct where the pstentces state tha" the general class of alloys contains silicon in suhsuntial amount. say from 3 to 15 per cent.) The alloy has, in the finished condition a tensile strength in the neighborhood of 84,000 pounds per square inch with an elongation of a 'iproxiinately 2 7 and a Brinnell hardness number of 80.

It will be observed that the die casting operation involves an incidental heating of the forging and that the properties of the forged alloy must be such as to entail no adverse effect resulting from such heating. While the preferred alloys have been stated, considerable latitude of choice is offered within the disclosure of the alloy patents above mentioned, and best results are secured by a careful coordination such as will ensure the use of two alloys, which considering the sizesand forms of the two parts, will in cooperation produce the desired result. It is quite possible that serviceable alloys not falling within the disclosures of said two patents may be found out the two specified have developed highly desirable characteristics in practice and are preferred.

The casting as it comes from the die includes the base plate 12 with pendant flange 13, the standards M and a connecting head 15 for each pair of standards. The openings 16 in the base plate have countersink margins .17 to receive cover glasses through which the verniers are viewed.

The casting; is snagged and the Vernier openings are finished to size and the centend-efini-ne" the axis on which the spindle blank was originally turned are reestablished and used in turning a new tapered surface on the spindle. Thereafter this surface or the centers are used :to position the frame in machining: operations which include,-facing' the lower portion of the base plate at 19 to receive the vernicrs; facing;- the'inner side of flange 13; machining shoulder 21; facing the heads 15; slotting" heads '15 to receive trunnion bearing blocks 22; mounting bearingr'caps includingdrillin holes for pins 2% and screws 25; drilling, reaming and hobbing the trunnion hearings in blocks 22 and caps 5. and drilling a number of holes and tapping certain of them. These holes include, for example, those indicated at 26 for the level posts, at 27 for the vertical circle VQZBlGIT, at 28 for the compass, and various others, as may be required by the design of the particular instrument.

As indicated in Fig. .3 one block 22 is vertically adjust-able and the tapped hole 30 is formed to receive the adjusting screw.

in the final hobbing operation a relief is out at 31 and later portions of the bearing in the cap are relieved at 32. The trunnion bearings are of the annularly grooved type for which no novelty is here claimed.

The final operation is to mount the frame on centers and turn and grindthe spindle to finished dimensions. As finished there is a relief groove 33.

' the spindle, as contradistinguished fromsubstantially the remainder ofthe frame,

It Will be observed that all the machining operations are referred to the axis of the spindle, and it follows that the accuracy of the finished productis dependent-solely on the operative precision of the machine tools used in its production. The frame structure is unitary with the exception of the inserted bearing blocks, and the bearing caps which are used to secure satisfactory bearing metal at these points.

Attempts have heretofore been made to use aluminum in the frames of surveying instruments to secure lightness, but these failed, first because the aluminum zinc alloy used Was soft, Weak and subject to spontaneous disintegration, and second, becausethe sectional construction used exaggerated the inherent defects of the material.

The strong alloys used according to the present invention have physical properties far superior to those of the bronzes and brasses customarily used in surveying instruments; they do notwarp as do some bronzes, they can be satisfactorily machined,

and they are light in weight. The unitary construction and heat treatment produce a frame relieved of all internal stresses, such as are inevitably present in sectional frames. The method of machining ensures precise accuracy, ensures symmetry of the cast portion relatively to the forged insert, and permits the elimination of various adjustments formerly necessary to correct errors inherent in any sectional construction. The result is strength, simplicity, lightness and maintained accuracy in a degree never before approached.

What is claimed is,

1. A frame for geometrical instruments of the light ray type, comprising a spindle name to this specification.

EDWARD W. ARMS.

composed of'mechanically worked and refined metal and a frame of cast metal permanently united with said spindle in the casting operation.

, 2. A frame for geometrical instruments of V the light my type, comprising a spindle'of mechanically worked aluminum-base alloy, and a head of cast aluminum-base alloy permanently united therewith by the casting operation.

3. A frame for geometrical instruments of the light ray type, including a spindle formed of a mechanically worked, quenched and artificially aged aluminum-base alloy free from copper except as an impurity, and containing magnesium and not less than 0.5% silicon, and a head of a different aluminum-base-alloy permanently united therewith.

4:. A transit frame, comprising in a single telescope standards, the metallic structure of 

